The overall objective of these studies is to develop improved procedures for the early detection of Legionnaires' disease bacillus (LDB), its products, and the host response to it. The approach will be to identify certain biological properties of LDB and their effect on diagnostic tests. Studies will utilize the type strains of the four recognized serogroups of LDB, each of which will be further categorized into four stages representing the in vivo form and three morphologically different in vitro forms. Each stage will be characterized by morphology, staining properties, cultural and nutritional characteristics, biochemical reactions, gas liquid chromatograms (GLC), and antigenic analysis. Antisera prepared to each of the stages will be studied with appropriate antigens to detect similarities and differences between stages and serogroups. Cultural, biochemical, and GLC characteristics will provide a basis for improving in vitro isolation techniques. Immunological properties, including the reactivity patterns of the various antigens and antisera, will be used to develop a rapid diagnostic test for LDB antigens in body fluids; and to improve the precision, sensitivity, and specificity of serologic tests for antibody.